Telephone-exchange system



' L. 'POLINKOWSKYQ TELEPHONE EXCHANGE SYSTEM. APPLICATION FILED MAY 2. 1919.

1,365,270. Patented Jan. 11,1921.

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L. POLINKOWSK'Y.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED MAY 2. 1919. 1,365,270. Patented Jan. 11,1921.

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TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED MAY 2. 1919.

. 1,365,270. Patented Jan. 11, 1921.

9 SHEETS-SHEET 3.

L. POLINKOWSKY,

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED MAY 2. 1919.

1,365 ,270. Patented Jan. 11, 1921. I 9 SHEETS-SHEET 4.

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TELEPHONE EXCHANGE SYSTEM. 7

APPLICATION FILED MAY 2. 1919.

' Patented Jan. 11, 1921.

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TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED MAY 2. l9l9.

Patented Jan. 11,- 1921.

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L. POLINKOWSKY.

TELEPHONE EXCHANGE SYSTEM. 'APPLICATION FILED MAY 2. 1919.

1,365,270. Patenfed Jan. 11,1921.

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Ljaa po/lhlfoms/fy L. POLINKOWSKY.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED. MAY 2. 1919. 1,365,270. 1 I

9 SHEETS-SHEET 9- Patented Jan. 11,1921.

UNITED STATES PATENT OFFICE.

LIPA. POLINKOWSKY, OF NEW YORK, N. Y., ASSIGNOR TO WESTERN ELECTRIC COM- PANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TEIiEPI-IONE-EXCHANGE SYSTEM.

To all whom it may concern:

Be it known that I, LIPA POLINKOWSKY, a citizen of Russia, residing at New York, in the county of New York, State of New York, haveinvented certain new and useful Improvements in Telephone-Exchange Systerns, of which the following is a full, clear, concise, and exactdescription.

This invention relates to telephone exchange systems in which connections be tween subscribers lines are established by means of machine switching apparatus.

More particularly it relates to a system of this character in which the subscribers lines are provided with toll devices, such as com collectors or message registers, operated by mechanism associated with and controlled by the switching apparatus to make a charge against calling subscribers lines of all calls that have been successfully completed.

The object of the invention is to provide, in a machine switching telephone system, the subscribers lines with toll devices with operating means therefor, and which operating means is arranged to cause the proper operation of said toll devices, according as a call succeeds or not, under the control of mechanism adapted to control the selective switches in the exchange.

A feature of the invention consists in providing a plurality of operating sources for the toll devices on the subscribers lines, together with means controlled by certain controlling apparatus associated with the selective switches, for determining which of sald sources shall be effective to operate the toll device, dependent upon whether or not the call succeeds.

A further feature consists in the-provision of a plurality of operating sources forthe toll devices, with means for determining the selection of said operating sources, and which means is controlled by mechanism used for controlling the selective operation of the. selective switches during the time such mechanism is restoring to its normal.

' position'on the release of a connection.

his

A still further feature of invention, in a system of this type where controlling switches are employedto control the operation of the, selective switches. is the provision of toll devices such as coin collectors at the substations, together with two sources of current, one for operating the coin collector to cash the coin and the other to return Specification of Letters Patent.

the coin, and means under the control of said controlling switches during release for selecting one or the other of said current sources.

Other and further features contemplated by the present invention will become apparent as thedescription progresses.

In the drawings, Figures 1 and 1 show circuits and apparatus of a subscribers line and a first line finder. There is also shown in Fig. 1, a coin collecting device at the substation together with means at the exchange for operating said device. Figs. 2 and 2 illustrate a second line finder, a group selector and the circuits and apparatus associated therewith. Figs. 3 and 3 show the circuits and apparatus of a final selector. Figs. 4 and 4* illustrate the circuits and apparatus of the register and controlling equipment adapted to be associated with the connecting circuit shown in Figs. 2 and 2 to control the selector switches. Fig. 5 shows a party line with coin collecting devices provided at each substation with means at the exchange individual to the line for controlling the operation of said devices. Figs. 1, 1, 2, 2*, 3, 3 4 and 4 taken together comprise a diagrammatic showing of a system involving the principles of this invention.

The figures should be arranged as follows: Figs. 1, 1 2, 2, 3 and 3 placed in order from left to right with Fig. 4 beneath Fig. 2, and Fig. 4 beneath Fig. 2". To'include the modification shown in Fig. 5 in the system disclosed, this figure may be substituted. for Fig. 1.

The line finders, group selectors and sequence switches are of the type already known in the art and need not be described specifically herein, it being suflicient to deusual type of switch only by the addition of two extra notches in the interrupter Patented Jan. 11, 1921. Application filed May 2, 1919. Serial No. 294,245.

between the two banks of line contacts, the

'interrupter plate at the top of the selector being made smooth over the portion thereof corresponding "to the space. In the final selector switches disclosed herein, however, two notches are cut in the interrupter plate 1 corresponding to the spacing between the banks for a purpose to be hereinafter described. That is to say, in selecting a line, in the first ten lines on a given level, the interrupter will operate a number of times corresponding to the number of lines passed over, whereas in selecting a line in the second set of ten contactson such level, the interrupter will operate a number of times corresponding to the number" of contacts passed over plus two. For a detailed description of the constructionand operation of a final selector switch of this character reference is made to the. patent of Polinkowsky, No. 1,193,053,'issued August 1, 1916.

The line finders, group Iselectonfinalselec tor, the controlling sequence switches therefor together with the register controlling equipment disclosed in said patent are in general similar in construction and operation to the apparatus comprising the system in which the present invention is embodied.

It is thought that the invention as disclosed herein will be best understood from a detailed description of the operation of the system shown. j

Assuming that the subscriber at the substation indlcated at 120 desires to converse with the subscriber at substation 320, whose number, for example is 307, he first inserts a coin 150 in the well-known manner in the slot of the coin collector at the substation and removes his receiver from the switch hook. A-circuit is therefore established for line relay 121 from battery through the winding of said relay, back contact and armature of relay 151, left-hand contact of relay 139 over the upper conductor of the line, through the winding of the operating ground. Magnet 152 being marginal does not operate, but the line relay 121 attracts its armature to close a circuit for the common starting relays 122.

.The relay 121 also closes a circuit from battery through the'inner windings of relays 122 to the multiple terminals 132 of all first line finders having access to the group containing the calling line, therebgi placing a selectable potential thereon. elays 122 complete a circuit from ground over their armatures and contacts, sequence switch contacts 104 of all idle first line finders in the group, armature and back contact of relays 137, sequence switch contacts 103 to the power magnets 123 of such line finders,

which therefore start in motlon moving their brushes 125, 126, 127 and 128 over the terminals 129, 130, 131 and 132 to search for the calling line in the usual way. As soon as one of these finders advances its brush 128 into contact with the terminal 132 of the calling line, a selectable condition will be found thereon and an energizing circuit completed for the right-hand high resistance winding of test'relay 135 over sequence switch contact 102 bottom, contact 108 top,

the second test relay 137 is removed at the interrupter brush 136, relay 137 energizes in series with the left-hand winding of relay 135 to ground at contact 106 bottom. The low resistance of this circuit so reduces the potential upon terminal 132 that the calling line is rendered non-selectable to other first line finders. Belay 137 by attracting its armature opens the circuit of the power magnet 123 and closes a circuit from ground, armatures and contacts of relays 122, sequence switch contact 104, armature and front contact of relay 137, contact 105 top, winding of the sequence switch magnet 100 to battery and ground and also in parallel therewith a circuit over sequence switch contact 153, winding of the holding magnet 138 to battery and ground. The holding magnet 138 brings the brush carriage to rest with the brushes accurately centered, while sequence switch 100 moves out of position 1 and into position 2. In position 2,,ground .is placed upon the terminal 132 over sequence switch contact 112 bottom" to maintain the calling line busy, the contact 102 having been opened when the se uence switch passed out of position 1. n the second position of contact 110, the cutoff relay 139 is energized causing the deener'gization of the line relay .121 and consequently the deenergization of the starting relays 122. provided no other line in the group is calling at this time. circuit from battery over-its right-hand armature and front contact, right-hand winding of slow-to-release relay 151 to ground which causes said relay .to energize. In parallel with the circuit for the cutoff relay 139, a circuitis closed for relay 154, which,

Cutoltrelay 139 also closes a however, being marginal, does not energize. The deenergization of relay 121 opens the battery circuit=tothe terminals 132 of the calling line and such line now having been seized. and being maintained busy, no selectable potential is possible upon the test terminals thereof. The sequence switch 100 oncoming into position 2 establishes a circuit from ground, contact 113, contact 602 bottom of sequence switch 600, armature and back contact of relay 237, contact 603 top,

through the winding of the power magnet tending from battery, resistance 141 contact 108 bottom, winding of relay 137, contact 106 top, contact 107 ,to the terminals 234.

When the brush 230 of one of the second line finders comes in contact with the terminal 234 upon which this selectable potential exists, the test relay 235 of such second line finder is energized in a circuit from battery, as traced to the terminal 234 and thence by way of brush 230, sequence switch contact 604' top, through the right-hand high resistance winding of relay 235, sequence switch contact 605 top, through the winding of the second test relay 237, se uence switch contact'606 top to ground. elay 235 energizes and closes a circuit for its left-hand low resistance winding in parallel to its right-hand winding, thus reducing the "potential upon the terminal 234 to render the connecting circuit busy to other second line finders. The second test relay 237 is short-circuited by a direct path to ground at the interrupter brush 236 and the brush carriage contiiiues to rotate until the brushes are accurately centeredat which time such short circuit is removed at the interrupter brush 236. Relay 237 energizesin series with relay 235. The relay 237, by attracting its armature, opens the above traced circuit for the power magnet 226 and closes a circuit for holding magnet 238, thus bringing the brush carriage to rest. At the same time, a circuit for sequence switch 600 "is closed in parallel to the circuit for holding magnet 238 and the sequence switch moves into its second position.

As the sequence switch 600 leaves its first position and until it is passed through its seventh position, a test guard is maintained upon the terminal 234 by the closure of the contact 610, connecting ground to such terminal.

As the sequence switch 600 was passing from its first to its second position, the contact 611 was closed sufiiciently long to drive sequence switch 200 out of position 1 and into position 2 over a circuit including se quence switch contact 202 bottom and contacts 611 top.

In position 2 of sequence switch 600 and in position 2 of sequence switch 200, the selection of an idle register will take place. Before considering this operation, however, the effect of the seizure of the circuit'connectedto the first line finder and the movement of sequence switch 200 into position 2 will be described. When the test relay 235 was energized, the-circuit therefor included the relay 137 at the first line finder. The relay 137 energizes and closes a circuit from battery to the winding of sequence switch magnet 100, contact 105 top, front contact and armature of relay 137 to ground at contact 104 l mztom, whereby sequence switch 100 moves from position 2 into position 5.

In position 5, the circuit of relay 137 in cludes thelresistance 140, contact 107 havin'g opened on leaving-position 4, as well as the resistance-141, but such relay will remain energized until sequence switch contact 610 leaves position 7 In position 5 of the sequence switch 100, the contact 110 being opened, the circuit for the cutoff relay 139 now includes the in its second position; In this position, the

contact 112 is opened and the circuit of the calling line is extended over contacts 210 top and 211 top. to the repeating coil 239. As the sequence switch 600cameinto its second position, the contacts 604 bottom, 619 top, 605 bottom, 606 bottom, and 613 bottom were closed. If, at this time, the sequence switch 700 individual to the connecting circuit shown, is in such position that an idle register is connected by said sequence switch to the leads shown, the relay 240. will be energized in a circuit from ground, sequence switch contact 703, winding of relay 240, contact 619 .top, winding of relay 235, contact 604 bottom, contact 7 04 bottom, winding of relay 426, contact 405 of the sequence switch 400 individual to such idle register resistance 490 to battery and ground. If, however, the equipment with which the leads are connected over such sequence switch 700 is already busy, the test circuit including the relay 240 of some other connecting c rcuit will alreadv be closed through the relay 426 and insufficient current will pass through the relay 240 shown to cause its energization. A circuit will therefore be established from battery through. the winding of sequence switch motor magnet 700', contact 702, contact 613 bottom, back contact and armature of relay 240 to ground; Sequence switch 700 thereupon moves out of the position in which it is standing and continues to move until it reaches a position in which the connecting circuit shown is associated with an idle register equipment at which time the relay 240 receives sufficient. current in series with relay 426 of. such idle equipment to energize. Relay 240 opens the circuit of the sequence switch 700 causing the same to stop and the relay 237 being energized in parallel with relay 240 closes a circuit from battery through the winding of sequence switch motor magnet 600, contact 607 top, front contact and armature of relay 237,. contact 602 top, back contact and armature of relay 242 to ground to drive sequence switch 600 from its second and into its third position. In this position, relay 240 and relay 237 are directly connected over contacts 619 bottom, and contact 704 bottom, for example as shown, to the starting relay 426. The idle registering equipment is now seized and is inaccessible to any other connecting circuit having access thereto until it has'performed its function or has been released by the replacement of the receiver of the calling subscriber.

As the sequence switch 600 moved into its third position, it closed a circuit over its contact 609 including contact 202 top, to drive sequence switch 200 into its third position. In the third position of sequence switch 200, the calling subscribers line is connected over contacts 211 and 210 bottom to the register controlling equipment ready for the transmission of impulses in accordance with the designation of the called line. The impulse circuit for setting the controlling registers may be traced from battery through the winding'of stepping relay 427, contact 402, contact 707, contact 210 bottom, brush 228, terminal 232, brush 126, terminal 130 over the loop of the substation 120 and returning by way of terminal 129, brush 125, terminal 231 brush 227 to ground at contact 211 bottom.

The relay 426 being energized as above described, a circuit is closed from ground at its right-hand armature and front contact, over contact 404 bottom to drive the sequence switch 400 out of position 1 and into posi-v tion 4.

It will be observed that the calling subscribers supervisory relay 241, which, at this time, controls the restoration and which, 1n positions 2 and 4 and positions. subsequent thereto, is directly under the control of the calling subscriber, is energized by the closure of contact 205 as sequence switch 200 comes into position 3, thus preventing relay 241 from effecting a premature release of the ap paratus. The mechanism will now await the sending of-impulses by the calling subscriber, such impulses being arranged 1n groups corat responding to the complement of the digits of the numerical designation of the called line, that is to. say, the called subscribers number being assumed to be 307, the calling subscriber will transmit to the central office three series of impulses, the first series comprising seven! impulses, the second series comprising ten impulses, and the third series comprising three impulses. In each of these series of impulses, the last impulse sent will be relatively longer than the other impulses of the series. The sender by which these impulses are sent may be of any desired construction provided that the impulses are sent in the complementary manner and that the last impulse of each group is comparatively longer.

The system herein disclosed is, for convenience, shown as a 1000 line system. In such a system there will be five groups of final selectors each accessible to 200 lines thereof, and the group selectors used will have only five of the ten banks utilized, one

bank of contacts being connected to the trunk lines of the group of final selectors individual to one group of 200 lines, another connected to another group of final selectors individual to another group-of 200 lines and so on.- In accordance with the translating system disclosed herein, the selection in the group selected, when the trunk line leading to the group of lines having the proper hundreds digit is such that if the hundreds digit of the desired line is O or 1, the tripping spindle of the group selector will be adjusted to release the proper set of brushes on the brush carriage by the movement of such spindle one step. If the hundreds digit of t e desired line is 2 or 3, the tripping spin le will be moved three steps. If the hundreds digit is 4 or 5, the tripping spindle will be moved five steps and so on. It will be understood that if the system comprises more than 1000 lines, the intermediate stages on the group selectors that is, the second, fourth, sixth, eighth and tenth will be reserved for use when a trunk line is desired leading to the groups of final selectors having access to lines in the second thousand. It will be further understood that by properly rearranging the tripping teeth on the spindle, the five levels and terminals which are used, may be arranged, if desired, adj acently to each other so that the first level will be selected by a single step of the tripping spindle, the second level by three steps of such spindle, the third level by five steps of such spindle and so on. Furthermore, any other preferred or desired method of grouping the lines may be used.

The operation, therefore, of the subscribers sending mechanism to send the hundreds digit. three steps will produce seven breaks in the circuit traced including the stepping relay 427, the last of such breaks being relatively longer than the others. Upon the energization of the stepping relay 427, a circuit was closed from ground over its armature and front contact, contact and righthand armature of relay 428, sequence switch contact 408 throuvh the lower winding of the hundreds register 429 to battery and ground. This causes the energizationof the power magnet of such register which moves only midway between its 0 and its first position where its local contact 471 is closed. At this time, a circuit is closed from battery through the upper winding of register 429, contact 471 to ground at the right-hand armature and front contact. of relay 426.

.The two windingsof the register are arranged in differential relation. to each other,

such that when both are energized, the reg-' ister will not move, whereas'when a circuit is closed through but one of such windings, the register is operated. The register 429 having, therefore, been brought to rest between its 0 and its first position will await the opening of the circuit through its lower winding at the front contact of stepping relay 427. Therefore, as the result of the first interruption in the circuit by the operation of the subscribers sender andthe consequent deenergization of the stepping relay 427, the hundreds. register willmove into its first position the circuit forthe upper winding thereof being also open as soon as the first position is reached by the local contact 471, whereupon the register sto s in position 1. Upon the cessation of the rst interruption, the relay 427 is again energized and register 429 is driven to a position intermediate of its first and second positions and correspondingly in response to the second interruption, it will be driven into its second position. Therefore, as the circuit is interrupted seven times upon the cessation of the seventh interruptlon, the register '42!) will be driven into its seventh position. this interruption is a longer one, the stepping relay 427 will be denergized sufiiciently long for the armature to close at its back contact, a circuit for the slow energizing relay 428," including sequence switch contact 413. Relay 428 being slow to act did not energize during the short-closures of its circuit at the back contact and armature of relay 427. The relay 428 opens the circuit of the register 429 at its right-hand armature, in orderto prevent a false operation-of such register and closes at its lefthand armature, a circuit including the contact 404 top to drive the sequence switch 400 out of position 4 and into position 6. The hundreds register has nowbeen set and it may proceed to control selection in the group selector. For this purpose,the outgoing sequence switch 450 shown to the right of Fig. 4 has been started by the closure of contact 407 bottom. as the incoming sequence switch 400 passed through its fifth position. Sequence switch 450 moves into its fourth position. Before, however, describing the selection operation initiatedby the movement of the outgoing sequence switch 450 further registering operations will be described.

Upon the reestablislnnent of the translast interruption of this group being relatively longer, the change-over relay 428 energizes and closes. a circuit over sequence switch contact 404 top to drive sequence switch 400 into position 8 to place the units register under the control of the stepping relay. The closure of the controllin circuit including stepping relay 427 and its interruption three times to send the complement of the digit 7, will cause the units register 431 to move into its third position in the manner now well understood, and

the final interruption being comparatively longer, relay 428 energizes and closes a circuit for driving sequence switch 400 out of position 8 and into position 9. The incoming sequence switch 400 will remain in its ninth position until, at the conclusion of the selection controlling operation, it is started in motion by a circuit closed by the outgoing sequence switch 450 returning to its normal position which will hereinafter be described.

The registershave now been set to properly control the selection in accordance with the numerical designation of the desired subscribers line, thehundreds register having been moved to its seventh position, the tens register to its tenth position and the units register to its third position. As the incoming sequence switch 400 reached its ninth position, a circuit was closed over contact 412 and contact 206 bottom to drive the sequence switch 200 out of its third and into its fourth position, in which position the supervisory relay 241 is again placed under the control of the calling subscriber and the impulse sending circuit is disconnected from the registers at the contacts 210 and 211 bottom.

The outgoing sequence switch 450in pass-' winding of the translating relay 432, contact 459 of sequence switch 450 closed in position 1%, contact 474 of the hundreds register 429. It having been found to be odd, the hundreds register being in its seventh position and the contact 474 consequently being closed, the translating relay 432 is energized. It will be observed that the contact 474 of the hundreds register is closed in the following positions, only a few of which, for convenience, are indicated upon the drawings:

% to l The relay 432 onenergizing closes a locking circuit over its right-hand armature and sequence switch contact 455, such relay remaining energized until the sequence switch 450 leaves its ninth position. As the sequence switch 450 passes through its second position, the closure and the subsequent opening of the circuit of the lower winding of the hundreds register 429 at sequence switch contact 458 bottom causes said register to take an additional step, that is, in this case, to be moved into its eighth position.

Also, as sequence switch 450 passes through its third position, the translating relay 432 being locked up, a circuit is established over the contact 460 top, left-hand armature of such relay and contact 461 bottom to drive the hundreds register 429 another step from its eighth to its ninth position;

The sequence switch 600 being already in its third'position, the fundamental circuit from the registering and controlling equipment is closed to the group selector shown on Fig. 2*. This circuit may be traced from battery throughthe winding of relay 242, contact612, contact 473 of the hundreds register 429, contact 457, winding of the stepping relay 433 to ground at contact 611. The energi'zation of relay 242 closes a circuit from ground over its armature and front contact, sequence switch contact 614, for the sequence switch 600, which thereupon moves from position 3 into position 4. In position 4 of sequence switch 600,

a circuit is closed for the tripping spindle,

power magnet 243 which includes the front contact and armature of relay 242. As the relay 433 was energized coincidentally with the energization of the line relay 242, it closed a circuit over sequence switch contact 458top for the lower winding of the hundreds register 429. The register therefore, moved a half of a position, that is, until the closure of the local contact 471 completed a circuit for the upper winding of the register. As the tripplng spindle of the group selector begins to rotate, it intermittently closes a circuit to ground for the line relay 242 in shunt of the stepping relay .433. Upon the first closure of this shunt circuit, relay 433 deenergizes and opening the circuit of the lower winding of the hundreds register permits such register to advance into its tenth position. From this'position, it will be moved intermediate of its tenth and eleventh positions when relay 433 is again energized as the tripping spindle comes into its set position to trip the first set of brushes of the group selector and in the continued motionof the tripping spindle a second deenergization of relay 433 takes place and the hundreds register is moved into its eleventh position. The register advances in this manner one position for each stage through which the tripping spindle passes until it reaches its 0 or normal position. In the 0 position ofthe hundreds register, the contact 473 is opened and not only will the stepping relay 433 remain denergized when connection to ground is broken by the tripping spindle, but also the line relay 242 will denergize, since both the fundamental circuit and the branch circuit therefor to ground at the trip ing. spindle interrupter contact are opened. elay 242 de'einergizing, opens the circuit for the power magnet 243 bringing the tripping spindle to rest in position to select the desired set of brushes. Such tripping spindle having moved three steps is in position to release the third set of brushes on the brush carriage, as it will be recalled that a trunk leading to the group of final selectors in which the desired line appears is to be found in thethird level of such group selector.

As the hundreds register reached its normal position, if the incoming sequence switch 400 is in its ninth position, that is, if tens and units registration isvcompleted, a circuit .will be closed from battery through the winding of the outgoing sequence switch magnet 450, contact 456, contact 472,

contact 410 to ground to drive sequence switch 450 into its sixth position, in which it is ready to control tensselection as soon as an idle trunk line to the proper final selector has been found and seized by the group selector as will be described. if the incoming sequence switch 400 has not reached its ninth position, the outgoing sequence switch 450 will remain in its fourth position moving to its sixth position as soon as sequence switch 400 reaches its ninth position.

When relay 242 released its armature, a circuit was closed from battery through the winding of sequence switch magnet 600, contact 607 bottom, back contact and armature of relay 237, contact 602 top to ground at the back contact and armature of relay 242 to drive sequence switch 600 into its fifth position. In this position, a circuit is closed for the group selector power magnet 244 eesmo from battery through the winding of such magnet, sequence switch contact 603 bottom, back contact and armature of relay 237, contact 602 top, to ground at the armature of relay 242. The brush carriage ofthe group selector begins to rotate, releases the selector set of brushes and moves them over the terminals of trunk lines of the level towhich they have access in search of an idle one thereof. So long as the test brush 247 makes contact with the test terline, full potential will be found thereon and a circuit is established from battery at the final selector over sequence switch con- .same non-selectable to other switches.

tact 312 bottom, contact 314 top, through the left-hand winding of relay 331 over the test conductor, test brush 247 of the group selector, right-hand high resistance winding of test relay 235, contact 605 top, through the winding of the second test relay 237, contact 606 top to ground. Relay 235 energizes, but relay 237 being shunted by a direct path to ground at the interrupter brush 269 of the group selector does not energize until the brushes are accurately centered upon the terminals of the selected trunk. Relay 235, by attracting its armature, closes a circuit through its left-hand low resistance winding in shunt of its high resistance winding, which thereby reduces the potential upon test terminal of the trunk line to render tllie s soon as the brush carriage has properly centered the brushes upon the terminals of the trunk, the relay 237'energizes and opens the above traced circuit for the power magnet 244 to bring the brush carriage to rest. The

operation of the relay 237 closes a circuit for the holding magnet 250 to insure the accurate centering of the brushes on the terminals of the trunk. This circuit may be traced from battery through the winding of said holding magnet, contact 608 top, contact 607 top, front contact and armature of relay 237, contact 602 top, to ground at the back contact and armature of relay 242. Relay 237 also closes'a circuit for the sequence switch 600 traceable from batterythrough the winding of the power magnet of such sequence switch, contact 607 top,

front contact and armature of relay 23 contact 602 top to-ground at the armature of relay 242. The sequence switch 600 moves from its fifth into its sixth position.

In this positionof the sequence switch 600, the fundamental circuit isclosed from the registers over sequence switch contacts 616 and 617 to the final selector, provided the outgoing sequence switch has reached its sixth position. When the sequence switch 450 was driven out of its fourth position upon the completion of the hundreds selection operation, it inoved directly into its sixth position, but in passing through its fifth position it closed a momentary circuit at contact 462 bottom for the lower winding of the tens register 430 to drive such register from its tenth into its eleventh positlon. When the fundamental circuit is closed in the sixth position of sequence switch 450 both relays 332 at the final selector and 433 at the register equipment are energized. The fundamentalv circuit may be traced from lay 332, contact "308 f" top, group selector brush 246, contactj617lbottom, contact 483 of the tens register, contact 453'top through the winding of stepping relay 433, contact 616 bottom, group selector brush 245 to ground at contact 309 top of the final selector sequence switch 300. The energization of relay 332 closed a circuit over sequence switch contact 303 top to drive sebattery through the winding of the line requence switch 300 into position 2. In position 2 of sequence switch 300, a circuit is closed for the tripping spindle power magnet 333 overcontact 302 bottom, to ground at the front contact and armature of the line relay 332. The brush trippingspindle begins to rotate in a well-known manner and as it passes through each brush trip ing position, the interrupter contact is c osedl to complete a momentary circuit for the line relay 332 in shunt of the step ing relay 433 at the register equipment. or each denergization of the stepping relay .433 the tens register is advanced a half position where it is subsequently moved to the full position in the manner above described.

It .will be recalled that the tens digit of the desired line is 0 and therefore such line is to be found in the first level of the finalselector. It will therefore be necessary that the selecting operation of the finalv selector opens the fundamental circuit at the spring 483 so that when the shunt circuit at the tripping spindle interrupter is opened both relay 433 and relay 332 are deenergized. At

the same time the closure of the contacts 482 of the tens register completes a circuit from ground, contact 411, contact 482, contact 463 top, through the .winding .of the outgoing sequence switch magnet 450 to battery to drive such sequence switch into its eighth position where it is ready to controltheunits selection. Upon the denergization of the line relay 332 of the final selector, the tripping spindle is stopped and a circuit is closed from ground, armature and back contact of relay 332, sequence switch contact 303 bottom, through the windingof sequence switch .magnet 300 to battery and this sequence switch moves from its second to its fourth position. As the outgoing sequence switch 450 passes through its seventh position, a momentary circuit for the lower winding of the units register 431 is closed at the contact 454 bottom to drive the units register an additional step or into its fourth position. The closure at this time of the fundamental circuit again energizes relays 332 and 433, but this time in the eighth position of se quence switch 300. In the fourth position of the sequence switch 300 a circuit is closed for the brush carriage power magnet 345 of the final selector including the contact 306 top and the front contact and armature of relay 332. In the initial movement of the brush carriage the proper set of brushes is tripped and in the continued movement thereof, such brushes are trailed over the sets of terminals individual to the lines appearing in this level of contacts. For each movement of the brushes to a set of terminals, the interrupter 337 closes in the well-known manner, a circuit to ground'for the linerelay 332 in shunt of'the stepping relay 433. The intermittent deenergization of relay 433 due to the shunting action of the interrupter 337 at the final selector causes the units register to be stepped through its successive positions. At the end of eight such operations of the relay 433, the

units register will be brought into its 0 or normal position, the selected brushes of the final selector at this time being about to make contact with the eighth or No. 7 set of contacts of the level to which they are indi- I vidual. It will be recalled, however, that since the desired line is located in an odd hundred, such line is to be found in the second half of the final selector bank and it is therefore necessary that the selecting operation should not terminate at this time. For this reason the fundamental circuit is not opened at the contact 493, as the register contact 453 bottom and thence throughthe stepping relay 433 as hereinbefore described. It will be recalled that the translating relay 432 was locked up when thesequence switch 450 passed from position 1 to position 2, since the hundreds register 429 was found in a position corresponding to an odd hundred. The fundamental circuit not being open at this time, the brush carriage on the final selector continues to move until the units register 431 has made a complete revolution. This means that the units register will take 12 additional steps. As has been hereinbefore mentioned, the interrupter segment of the final'selector is provided with two additional notches located between the first and second groups. 'In the case as is herein being described that the desired line is located in the second group, at the final selector it is necessary that the units re ister should be driven through a com ete cycle after having been restored to norma before it can open the fundamental circuit and since, such register is provided wlthtwelve positions, it becomes necessary to arrange for two additional steps. For this purpose,-

the extra notches are provided in the interrupter plate. This arrangement is clearly- As the units register 431. passed through its normal position the first time without stopping, a circuit was closed from batter through the winding ofthe sequence switc magnet 450, contact 463 bottom, contact 492 to ground. The outgoing sequence switch 450 thereupon moved from its eighth to its tenth position. On leaving its ninth position, the locking circuit for the translating relay 432 is opened permitting said relay to deenergize and also the sequence switch contacts' 460 bottom and 461 top are opened. Therefore, when the units register reaches its normal position, the above traced shunt around the contact 493 which previously maintained the fundamental -circuit closed, is now opened and consequently the step.- ping relay 433 is denergized and also t e line relay 332 of the final selector as soonas the brushes are accurately centered upon'the terminals of the desired line. The units register 431 on reaching its normal position, closes a circuit including its contact 492 and sequence switch contact 463 'to' drive the outgoing sequence switch from position 10 to position 1. As the sequence switch 450 passes through the position 11, a circuit is closed including sequence switch contact 455 bottom and contact 407 top to drive their,

longer required for this. connection the sequence switch 400 on leaving its ninth position opens the circuit of the relays 426 and 240 at the contact 406, which circuit had been substituted for the one ori 'nally established over the contact 405.- elays 426 and 240 are deenergized. 'The denergization of relay 426 and the restoration of the sequence switch 400 to normal will cause the registering equipment shown on Fig. 4 to' test -idle and accessible to any connecting circuit taken for use which has access to the same. .At the same time that relay 426 is deenergized, relay 240 also denergizes and closes a circuit including the sequence switch contact 613 to drive the sequence switch 600 out of itssixth position and into its seventh position, which is the talking position for this sequence switch. As sequence switch 600 passes from position 6 to.7,a momentary circuit is closed atcontact 611 top which also includes contact 202 bottom to drive the sequence switch 200 out of position 4 and into position 5. The sequence switches 200 and 600 remain in these positions awaiting further-operations of the final selector mechanism.

Upon the deenergization of the relay 332, a circuit is closed including sequence switch contact 303 bottom to drive sequence switchas sequence switch 300 moves from its fourth to its fifth position, the contact314 top is opened and 314 bottom' is closed. Relay 331 is maintained energized, both of its windings being now included in the circuit and battery is connected over the contact 314 bottom through the test relay 339. At the same time, the contact 307 top is closed, connecting battery with the high resistance right-hand winding of test rela 349. The fifth .positionof sequence switc. 300.. is the testing position thereof. If, in

this position full potential is found on the test terminal 3420f the called line indicating that ,the line is idle, the test relay 349 energizes. If, on "theother hand, the normal potential upon such test terminal 342 is reduced by such, line being busy, either as a calling line or as a called'line, the test relay 349 does not energize Assuming first that the line is idle and the test relay 349 consequently energized, it closes a circuit from battery, right-hand armature and contact of relay 331, contact 314- bottom through the winding of relay 339, left-hand low resistance winding of relay 349 to the test terminal 342 of the called line. i of this circuit which is in parallel to the ci-rcuit including the right-hand high resistance winding of; the test relay 349 is sulficiently low to cause a reduction of the potential on the test terminal 342, thus rendering the called line busy to other selectors. Relay 339 also energizes and as soon as sequence switch 300 reaches its sixth position, it will find a circuit closed over contact 305 bottom, front contactand armature of relay 339 ,to ground at the back contact and armature of relay 332. Sequence switch 300 therefore moves into position 10. A second circuit is also closed at the contact 317 to drive sequence switch 300 off position six and into position ten. :The sixth position The resistance of this sequence switch is provided for hunting an idle line to a private branch exchange in case the particular line selected is found busy. The apparatus for performing this operation is not shown, however, and in order to drive the sequence switch through its sixth position, which is, as shown, an idle position where the desired line is found idleor busy, the contact 317 is provided.

On reaching position 10, sequence switch 300 immediately passes to position 12, by means of the above traced circuit which is closed at the contact 305 in positions 10 and 11.

The 12th position of the sequence switch 300 is the ringing position. Current from the ringing source is projected over the called line in a circuit including the ringing relay 343 and sequence switch contacts 310' visory relay 248 in a circuit including battery and the right-hand windings of the repeating coil 239. Supervisory relay 248 by attracting its armature, closes a circuit from round, armature and front contact of said to battery'to drive such sequence switch out of. position 5 and into position 8. In position 8, the callingsubscriber would receive a busy tone by reason of the fact that the secondary winding of the busy tone machine is bridged across the line by'the closure of sequence switch contacts 212 and 213, were it not that almost immediately. thereafter the sequence switch 300'passes through position 11% causing a secondary momentary energization of called line supervisory relay 248. Relay 248, in energizing, a second time closes a circuit as above described 115 relay, contact'206 top,'through the winding of the sequence switch magnet 200 I 343 is sufficiently reduced to. permit the energization thereof in the well-known manner and which, on attracting its armature, closes a circuit over the sequence switch contact 305 top to drive the sequence switch 300 into position 13. In position 13, the talking circuit is completed from the repeating coil 239 through to the called line by means of the contacts 310 and 311. Relay 248 is therefore again energized and closes a circuit as above described including the contact 206 to drive sequence switch 200 out of position 11 and into position 14. The sequence switch 100 being in its fifth position, the sequence 200 being in its fourteenth position, the sequence switch 600 being in its seventh position and the sequence switch 300 being in its thirteenth position, the calling subscriber and the called subscriber are now connected for conversation, talking battery being supplied over the windings of the repeating coil 239.

The operation described is the normal operation of the system in which an idle line is selected, seized and signaled and the called subscriber responds. In such an operation it will be observed that the called 7 line supervisory relay 248 is energized three times,'first to move the sequence switch 200 from position 5 to position 8, then from position 8 to position 11 and finally from position 11 to position 14. The effect of these operations will appear hereinafter. Disconnection may take place under the control of either subscriber. The call having been successful the call should be charged to the calling subscriber, whether both subscribers restore their receivers to the hook or only one of them does so regardless of whether such subscriber is the calling or the called subscriber. If the calling subscriber should be the first to replace his receiver, the deenergization of relay 241 closes a circuit from ground, contact 352 top, contact and armature of relay 241, contact 209 bottom through the winding of sequence switch magnet 600 to drive such sequence switch from its seventh to its eighteenth position. Similarly the restoration of the called subscribers receiver to the switchhook causes the denergization of relay 248 which closes a circuit from ground, armature and contact of said relay, contact 4203, contact 209 bottom to drive sequence switch 600 from position 7 to position-18.

tracting its armature, closes a circuit from.

ground, contact 104 bottom, armatureand back contact of relay 137, contact 105 bottom to the winding of the sequence switch magnet 100 to battery and ground to drive such sequence switch out of position 5 and into position 9. As sequence switch 600 moved into position 8, it closed a circuit from battery, through the winding of the magnet of sequence switch 200, contact 202 top to ground at the contact 609 to drive sequence switch 200 out of position 14 and into its normal position. It will be observed that the sequence switches 600, 200 and 100 are simultaneously moving, the sequence switch 600 having started from its seventh position, the sequence switch 100 having started from its fifth position and the sequence switch 200 having started from its fourteenth position. Therefore' as the sequence switch 200 is passing through its fifteenth, sixteenth and seventeenth positions, the sequence switch 100, during a part of this time will not have reached its ei hth position. Hence, a circuit is closed rom the high potential battery 298, sequence switch contact 207 closed from positions 15 to 17, brush 229, terminal 233, right-hand winding of relay 135, contact 102, closed from positions 2 to 7 brush 127, contact 131, through the winding of the marginal relay 154 to ground. This increased battery potential causes the energization of relay 154 which in turn closes a circuit from the positive pole of battery, contact and armature of said relay, left-hand armature and front contact of cutofl' relay 139 over the upper conductor of the calling line through'the winding of the polarized magnet 152 through the coin 150 to ground. Currentof this polarity flowing through the magnet 152 causes the same to operate its armature in such a manner as to collect the coin which,at thesame time, opens the circuit just traced to cause the deenergization of themagnet 152. The calling subscriber is thus charged for having completed a successful connection to the called line.

'On coming into its eighteenth position, sequence switch 600 established the. usual restoring circuit for the brush carriage of the group selector which may be traced from batteryto the winding of power magnet 244, contact 603 bottom, back contact and armature of relay 237, contact 602 top. to

ground at the armature of relay 242. The

brush carriage rotatesland upon reaching its normal or home position, a circuit is closed from battery, contact 618, brush 269 in its home position, winding of relay 237, contact 606 top to ground. Relay 237, by energizing, stops the movement of the brush carriage in the usual manner and also closes a circuit from ground, armature and back contact of relay 24,2, contact 602 top, armature and front contact of relay 237, contact 607 top through the winding of sequence switch magnet 600 to battery to drive said sequence switch out of position 18 and into its normal position 1.

If the calling subscriber has not replaced. his receiver on the hook, the sequence switch 100 in passing into its eighth position, as above described again closes a circuit for relay 137 which energizes and opens the circuit, which started sequence switch 100 out of position 5 so that said sequence switch will stop in position 9, since it would otherwise continue to move by reason of the fact that contacts 104, and-105 are closed iiithis position. The circuit for the energization of relay 137 may be traced from battery, over the contact 108 bottom, through the winding of relay 137, contact 1.11 closed in position 8, over the lower side of the line, through the loop at the substation 120 and returning over the upper side of the line to ground at contact 112 closed in position 8. As soon, however, as the calling subscriber replaces his receiver to the switchhook, this circuit is opened and relay 137 by retracting its armature closes the above traced circuit to drive sequence switch 100 out of position 9 and into position 1. It will be observed that the cutoff relay 139 is maintained energized in the seventh position of sequence switch 100 in a circuit including contact 102 top, and in positions 8 and 9 in a circuit iiicluding resistance 199 and sequence switch contact 110 bottom. This control of the cutofi relay is transferred to the first line finder prior to the time that the original energizing circuit for said relay is opened by sequence switch contact 207 at the second line finder leaving its position 17 to insure the maintenance of the energization of said relay.

As the sequence switch 600 left its seventh position, it opened at the contacts 605 and- 606, a circuit, for the relay 331 at the final selector. This relay, therefore, deenergized and closes a circuit, from ground over its left-hand armature, contact 308 bottom through the winding of relay 332 to battery and ground. Relay 332 closes a circuit from ground over its armature and front contact, sequence switch contact 303 through the winding of magnet 300 to battery and ground whereupon said sequence switch moves fromposition 13 into position 16. ()n reaching position 16, the line circuit being open at the called subscribers substation, relay 332 deenergizes and closes a cir- -c'ontact 610 bottom.

" cuit from ground over its armature and back contact 303 top to drive seqli ience switch 300 into its normal position. he entire apparatus is now restored. It will be observed that although the relay 331 at the final selector is deenergized, as soon as sequence switch 600 leaves its seventh position, it is not again energized by the closure of the contact 610 bottom, as such relay 331 controls through its right-hand armature, its cord energizing circuit in all positions except position 1, of the sequence switch 300. In position 8 to 17, a busy condition is maintained on the terminal of the trunk line leading to the final selector by the closure of the At the final selector, when the sequence switch 300 comes into its fifteenth and sixteenth positions, it the called subscriber has not yet restored his receiver to the switchhook, a circuit will be established for the relay 332 traceable from battery through the winding of said relay, contact 308 top, contact 310, brush 335, terminal 341 over the loop of the called line and returning by way of terminal 340, brush 334, contact 311 top to ground at contact 309 top. Therefore, when sequence switch 300 reaches position 16, it will remain there, since the above traced circuit for driving it out of position 16, is now opened .at the armature of the relay 332, which is ener' gized, due to the fact that the called subscriber has not replaced his receiver to the switchhook. When the called subscriber hangs up his receiver, the relay deen ergizes' and closes a circuit as described todrive sequence switch 300 out of position 16 and into position 18.

Itwill now be assumed that the called line is busy at the time that it is attempted to establish a connection therewith. The group and final selectors having been selectably controlled by the register cont-rolling equipment in the manner already described 'to extendt-he calling line and the brushes 

